Invasions I

If I didn’t know better, and I had to bet whether a flaccid grass could outcompete a blackberry capable of flinging its spine-studded canes 20 feet up into the crowns of trees, I’d have bet on the blackberry. I probably wouldn’t have thought about either invasive species, honestly, living as I do in the lush belt of coastal forest in western Oregon, whose understory used to be dominated by shiny Oregon grape, shaggy ninebark, and the sturdy upflung arms of the sword fern. But I turned around in the last five years and the ferns were gone. 

In fact, the grass wins, by exuding chemicals from its roots that cut off its competition far below the knees. If the enemy of my enemy is my friend, I should love the grass that overwhelms the blackberry. Instead, there is an army marching in on the forests of my home, one that might well bring down even the massive trees. We know that invasive species can utterly overwhelm native vegetation, change ecosystem dynamics, and thus alter entire landscapes. They can be plants, insects, fungi, viruses, or even birds or mammals or snakes. Think kudzu, gypsy months, white-nose syndrome or sudden oak death, the starling, the wild pig, or the python in the Everglades. It’s the sort of overwhelming problem that might make you think that somebody, somewhere, must surely be doing something about it.

By and large, we are not. In fact, we rarely track the spread of even the most egregious invasive species, as a quick visit to the various state databases revealed to me. A glance out my window revealed the gaps, as the mass of invasive ox-eye daisies offered up a white-mouthed hoot of derision at the scanty occurrence map on my computer. They aren’t even in my county, according to the Authorities. Yet here they are, drifting thickly across my pasture. Almost none of the invasive species on my small farm are documented to be here.

Worse, we know even less about the consequences, particularly in a world facing climate change as well as the rapidly spreading army of non-native species. My colleagues and I reviewed hundreds of scientific papers dealing with climate change and invasive species. Almost none of them were based on hard experimental data. Instead, they were mostly limited to computer projections of climate models, themselves subject to considerable revision as more data are obtained. In sum, we have no idea how climate change will interact with and affect the rapid spread of invasive plants, animals, insects, and disease. The little data that do exist suggest that native species and habitats will not be favored. How this extraordinary, reckless experiment in shifting biota and climate will play out is not a matter of academic interest only; everything from food and fiber, fire and rainfall, ecosystem services from nitrification to pollination, hang in the balance. 

Yet our efforts are at best perfunctory, dealing only with the most egregious invaders in a rear-guard action that can only fail. Boats carrying zebra mussels are frequently found just before they are lowered down the boat ramp. You can buy an incredible array of invasive species on the internet, and release them, undetected, when you tire of them. Entire neighborhoods of Oregon’s largest city are being subjected to mandatory chemical treatment for an infestation of Japanese beetles, whose spread was facilitated by a regrettable cut in funding for monitoring. It goes without saying that treating the infestation is costing orders of magnitude more than was saved. Each day, more cargo unloaded from ships and planes that have traveled from all parts of the globe may carry new invaders. At some point, we’ll have to ask ourselves just how addicted we are to this high-stakes game of biological substitution speeding in on the wings of cheap and easy transportation, globalization, and free trade, unfettered by any considerations of collateral damage.

I spent the winter cutting blackberry along the creek. I uncovered trees and light-starved stands of snowberry, freed the branches of ninebark and Indian plum. But there were no more ferns, and along the newly revealed stream banks, the forward scouts of false brome are infiltrating the cow parsnip. The enemy of my enemy is still my enemy. I can’t begin to know how all the shifting balance of species and processes will affect even this small bit of creek bank, let alone what the occupying armies will create out of the wreckage of the world we knew. But we need to start asking the questions, and seeking the answers as quickly as we can.